Ciguatera was named, according to historical lore, by a 19th-century Englishman who became violently ill after dining on barracuda from Cuba. (Ciguatera, a Spanish reworking of the English “seawater,” was the word he used when implicating the fish.) It is present in the muscles and organs of more than 400 species of tropical reef–dwelling fish, especially those at the top of the food chain, such as grouper, red snapper, amberjack, and barracuda. Once again a unicellular microalga—in this case, Gambierdiscus toxicus—previously ingested by the fish is the ultimate source of the injurious toxin.
Within two to six hours of eating a ciguatoxin-tainted fish, most people develop a host of intestinal and neurological symptoms ranging from nausea, vomiting, diarrhea, and abdominal pain to shortness of breath, profuse sweating, staggering gait, vertigo, blurred vision, and abnormal sensations in the hands and feet. In some patients the symptoms disappear after 24 hours. In others they last for months.
Cases like Ronnie’s are far from rare. Experts in foodborne diseases know that ciguatera fish toxin is widely distributed throughout the South Pacific, the Caribbean, and other warm tropical waters. In fact, ciguatera is thought to be the most common form of seafood poisoning in the world, causing up to a million cases a year. But what is familiar to toxicologists is less well-known to medical practitioners. The challenge to clinicians, therefore, is to connect the dots in a given patient and reach the diagnosis on the basis of clinical and circumstantial evidence. Chemical assays are available to detect ciguatoxin in fish, but few if any doctors and nurses—especially in poor small towns—have access to such tests. Moreover, there are no specific tests to confirm the condition in humans.
In the end, Ronnie accepted my diagnosis. She was not happy to learn there is no “magic bullet” for ciguatera—I and other doctors would simply have to nurse her through her lingering symptoms—but she took comfort in knowing that the toxin would not cause permanent harm. Sure enough, over time she bounced back.
Today, despite the many healthful benefits of seafood, does Ronnie still eat fish? Not on your life. Cholesterol be damned; she’d rather take her chances with a steak.
Claire Panosian Dunavan is an infectious diseases specialist at UCLA Medical Center and past president of the American Society of Tropical Medicine and Hygiene. The cases in Vital Signs are real, but names and certain details have been changed.
